Fluid delivery device
Field of the disclosure
The disclosure relates to the field of fluid delivery devices.
Background
It is known to deliver small volumes of fluids, such as therapeutic fluids, using a pump. For example, insulin patch pumps may be used to deliver insulin into a person’s body. Such pumps may also be used to administer other therapeutic products to the human body. The pump may have an adhesive base, so that in use the pump sticks to the user’s skin and protrudes from the skin. Conventionally, the therapeutic fluid is delivered by use of a mechanical force to pressurise a reservoir containing the therapeutic fluid. For example, a spring might be used to depress a piston, pressurising a reservoir. For small doses and/or low delivery rates, the delivery rate of the therapeutic fluid may be controlled using a passive flow restrictor, such as an orifice or microcapillaries. For higher doses and/or delivery rates, a separate delivery mechanism may be used to control the delivery of the therapeutic fluid. Such separate delivery devices are typically bulky.
Reducing the size of therapeutic fluid delivery devices improves the convenience to the user. It is also beneficial, when dispensing insulin or other therapeutic fluids, to be able to ensure that an accurate dose of fluid is dispensed by the pump. Pumps may be used to deliver controlled volumes of fluid in other non-therapeutic applications, in which a reduced size of the fluid delivery device and an accurate dispensing volume are beneficial.
Summary of the disclosure
Against this background, there is provided a pump for dispensing fluid, the pump comprising a variable-volume chamber comprising an inlet and an outlet, wherein the chamber is configured to be in fluid communication with a reservoir via the inlet. The pump further comprises an aperture. The pump further comprises a first diaphragm filling the aperture and defining a portion of a boundary of the chamber. The pump further comprises a first deformable element adjacent to the first diaphragm. The pump further comprises a first shape memory alloy element coupled to the first deformable element and configured, on actuation, to deform the first deformable element such that the first diaphragm bends and the volume of the chamber changes, wherein the first shape memory alloy (SMA) element is parallel to a plane of the aperture.
In this way, fluid may be drawn into and expelled from the variable volume chamber by controlling the length of the shape memory alloy (SMA) element. The SMA element being parallel to the aperture provides a compact pump, with a relatively flat profile. Furthermore, the contraction of the SMA element is parallel to the aperture, but may result in a displacement of the diaphragm that is not parallel (e.g. perpendicular) to the aperture. The magnitude of the displacement of the diaphragm may be smaller than the magnitude of contraction of the SMA element, allowing for precise control of the displacement of the diaphragm by controlling the length of the SMA element. As a result, the quantity of fluid dispensed can be precisely controlled. The pump may be used to dispense a therapeutic fluid or other fluid.
As mentioned above, the pump comprises an aperture. The pump may comprise a housing which defines the aperture.
Also as mentioned above the first SMA element is parallel to a plane defined by the aperture. The SMA element may instead be defined as being parallel to the first diaphragm. The diaphragm may be generally planar and the first SMA element may be parallel to a plane in which the diaphragm lies when in a neutral state.
In some embodiments, the first SMA element may be at an acute angle to the plane defined by the diaphragm and/or a plane defined by the aperture.
The pump may further comprise an inlet valve having an open state enabling flow of the fluid into the chamber from the reservoir via the inlet and a closed state preventing flow of the fluid into the chamber from the reservoir via the inlet; and an outlet valve having an open state enabling flow of the fluid out of the chamber via the outlet and a closed state preventing flow of the fluid out of the chamber via the outlet. The inlet and outlet valves may assist in controlling the pumping of fluid into and out of the chamber.
The inlet valve may be an active valve. In other words, the inlet valve may be driven by an actuator to open and close. The actuator may comprise one or more SMA elements or another actuator,
The pump may comprise a second deformable element and a second shape memory alloy element coupled to the second deformable element and configured, on actuation, to deform the second deformable element to transition the inlet valve between the open state and the closed state. In this way, the inlet valve may be an active valve, in particular controlled by SMA.
The pump may further comprise a second diaphragm and the inlet valve may comprise an aperture. The second deformable element may be configured to deform so as to bend the second diaphragm to fully or partially block the aperture. In this way, the inlet valve may be provided by an aperture and a second diaphragm deformed by a second deformable element to block the aperture, thus closing the inlet valve.
The outlet valve may be an active valve. In other words, the outlet valve may be driven by an actuator to open and close. The actuator may comprise one or more SMA elements.
The pump may comprise a third deformable element and a third shape memory alloy element coupled to the third deformable element and configured, on actuation, to deform the third deformable element to transition the outlet valve between the open state and the closed state.
The pump may further comprise a third diaphragm and the outlet valve may comprise an aperture. The third deformable element may be configured to deform so as to bend the third diaphragm to fully or partially block the aperture. In this way, the outlet valve may be provided by an aperture and a third diaphragm deformed by a second third deformable element to block the aperture, thus closing the outlet valve.
The second diaphragm may be integral with the first diaphragm. The third diaphragm may be integral with the first diaphragm. Each of the first, second and third diaphragms may be provided by a single, common sheet of material. In other embodiments, each of the first second and third diaphragms may be separate. Alternatively, two out of the three may be provided by a single sheet of material, with the third being separate.
In some embodiments, the inlet valve and/or the outlet valve may be passive. In other words, the relevant valve may be driven to open and close by pressure differentials and not, for example, by an externally driven actuator.
The pump may further comprise a valve diaphragm comprising the inlet valve and the outlet valve.
In this way, a simple and compact valve arrangement may be provided.
The inlet valve and the outlet valve may comprise flaps in the valve diaphragm.
In this way, the inlet valve and the outlet valve may open in response to flow of fluid resulting from pressure differences.
The pump may comprise a support structure. The support structure may otherwise be referred to as a housing. The first shape memory alloy element may be connected between the support structure and the first deformable element.
The shape memory alloy element may be connected between a first coupling point and a second coupling point of the first deformable element. In this way, the SMA element is only coupled to the first deformable element (e.g, both ends of the SMA element may be coupled to the deformable element) and not, for example, connected between the housing and the first deformable element.
For example, the shape memory alloy element may be coupled to the deformable element via a first crimp and a second crimp.
Crimps may provide a secure attachment for the shape memory alloy element. The crimps may be integral to the deformable element, simplifying manufacture. The first crimp and the second crimp may each be configured to provide electrical connections to the shape memory alloy element such that an actuating current can be provided through the shape memory alloy element.
The pump may be configured such that on actuation of the shape memory alloy element, the first coupling point and the second coupling point are pulled towards one another. Actuation of the shape memory alloy element may result in bending and/or pivoting of the deformable element.
The first coupling point may be disposed on a first part of the first deformable element and the second coupling point may be disposed on a second part of the first deformable element. The first part and the second part of the deformable element may be partially attached to the diaphragm, such that on actuation the deformable element pulls the diaphragm. The first and second parts may be each electrically conducting and separated by an electrical insulator.
The shape memory alloy element and the deformable element may be external to the chamber. In this way fluid in the chamber is not exposed to the heating of the shape memory alloy element.
The first deformable element may comprise a flexure. The flexure may be elongate and have a longitudinal axis. The flexure may be flexible in a direction perpendicular to a direction perpendicular to the longitudinal axis of the flexure.
The inlet valve may be configured to open only in a direction to enable fluid flow into the chamber.
In this way, back-flow of fluid may be prevented.
The pump may further comprise a first end-stop configured to prevent the inlet valve opening in a direction to enable fluid flow out of the chamber.
The outlet valve may be configured to open only in a direction to enable fluid flow out of the chamber. In this way, back-flow of fluid may be prevented.
The pump may further comprise a second end-stop configured to prevent the outlet valve opening in a direction to allow fluid flow into the chamber.
The shape memory alloy element may be configured, on actuation, to deform the deformable element such that the diaphragm bends in a first direction. The pump may further comprise a second shape memory alloy element coupled to a second deformable element and configured, on actuation, to deform the second deformable element such that the diaphragm bends in a second direction.
In this way, the pump may be independently operated to either draw liquid into the chamber or to expel liquid from the chamber. Actuation of one shape memory alloy element may reduce the volume of the chamber, and actuation of the other shape memory alloy element may increase the volume of the chamber.
The first shape memory alloy element may be configured, on actuation, to deform the first deformable element in a first direction. The pump may further comprise a fourth shape memory alloy element coupled to the first deformable element and configured, on actuation, to deform the first deformable element in a second direction. In this way, the pump may comprise a pair of opposing SMA wires (the first and fourth wires) which drive the first deformable element to bend in different directions. Contraction of the first SMA wire may cause the fourth SMA wire to extend. Advantageously, the opposing wires afford better control over the diaphragm and hence fluid flow.
Alternatively, the pump may comprise a resilient element, e.g. a spring, which is configured to oppose contraction of the first SMA element. In some embodiments there may be no resilient element or an opposing SMA element present. Instead, one of or a combination of elasticity of the diaphragm itself and fluid pressure may return the diaphragm to its unstressed state when the first SMA element is not contracted (i.e. no longer powered).
The second shape memory alloy element may be configured, on actuation, to deform the second deformable element in a first direction. The pump may further comprise a fifth shape memory alloy element coupled to the second deformable element and configured, on actuation, to deform the second deformable element in a second direction. The pump may therefore comprise a pair of opposing wires to drive movement of the second deformable element, with the same benefits as described for the first deformable element.
The third shape memory alloy element may be configured, on actuation, to deform the third deformable element in a first direction. The pump may further comprise a sixth shape memory alloy element coupled to the third deformable element and configured, on actuation, to deform the third deformable element in a second direction. The pump may therefore comprise a pair of opposing wires to drive movement of the third deformable element, with the same benefits as described for the first and second deformable elements.
The first direction may be opposite to the second direction.
Any of the means for returning the first diaphragm to its unstressed (unbent) state described above with reference to the first diaphragm may also be applied to the second and/or third diaphragms.
On actuation, the first deformable element may push the diaphragm. The first deformable element may be coupled to an engaging portion which engages with and pushes the first diaphragm. The first diaphragm may be connected to the engaging portion such that the engaging portion is configured to also pull the first diaphragm. The second and/or the third deformable elements may be configured in the same way.
In this way, actuation of the shape memory alloy element may result in bending of the diaphragm, without need for any attachment between the deformable element and the diaphragm.
The deformable element may comprise a first part coupled to a first end of the shape memory alloy element and a second part coupled to a second end of the shape memory alloy.
In this way, in certain arrangements the contraction of the shape memory alloy element may deform the deformable element towards the shape memory alloy element. In other arrangements, the contraction of the shape memory alloy element may deform the deformable element away from the shape memory alloy element. In certain arrangements, the first part and the second part may not be electrically connected. The first part and the second part of the deformable element may be partially attached to the diaphragm, such that on actuation the deformable element pulls the diaphragm.
The first and second parts may be electrically conducting and separated by an electrical insulator.
In this way, an electric current may be applied through the shape memory alloy element by applying electrical connections to the first and second part of the deformable element.
There is also provided a valve assembly for controlling fluid flow. The valve assembly comprises: a support structure defining an aperture; a diaphragm adjacent to the aperture; a first deformable element adjacent to the diaphragm; and a first shape memory alloy element coupled to the first deformable element and configured, on actuation, to deform the first deformable element such that the diaphragm bends and aperture is partially or completely blocked by the diaphragm.
Accordingly, the principles described above in the context of a pump may also be applied to a valve assembly. Any of the features above described with reference to a pump (e.g. SMA element arrangements) may be applied to a valve assembly.
The shape memory alloy element may be parallel to a plane of the aperture. The SMA element may instead be defined as being parallel to the first diaphragm. The diaphragm may be generally planar and the first SMA element may be parallel to a plane in which the diaphragm lies.
In some embodiments, the first SMA element may be at an acute angle to the plane defined by the diaphragm and/or a plane defined by the aperture.
The first shape memory alloy element may be configured, on actuation, to deform the first deformable element in a first direction. The valve assembly may further comprises a second shape memory alloy element coupled to the first deformable element and configured, on actuation, to deform the first deformable element in a second direction. In this way, the valve may be driven by a pair of opposing wires.
There is also provided a method of dispensing fluid using a pump. The pump comprises a variable-volume chamber comprising an inlet and an outlet, wherein the chamber is configured to be in fluid communication with a reservoir via the inlet. The pump further comprises an aperture. The pump further comprises a diaphragm filling the aperture and defining a portion of a boundary of the chamber. The pump further comprises a deformable element adjacent to the diaphragm. The pump further comprises a shape memory alloy element coupled to the deformable element and configured, on actuation, to deform the deformable element such that the diaphragm bends and the volume of the chamber changes, wherein the shape memory alloy element is parallel to a plane of the aperture. The method comprises actuating the shape memory alloy element such that the volume of the chamber changes from a first volume to a second volume and liquid flows through the chamber in a first direction; and allowing the shape memory alloy element to relax such that the volume of the chamber changes from the second volume to the first volume and liquid flows through the chamber in a second direction.
Brief description of the drawings
A specific embodiment of the disclosure will now be described, by way of example only, with reference to the accompanying drawings in which:
Figure 1 shows a schematic diagram of a perspective view of a pump according to an embodiment of the present disclosure.
Figure 2 shows a schematic diagram of a cross-section of a pump according to an embodiment of the present disclosure.
Figure 3 shows a schematic diagram of the pump of Figure 2, with the inlet valve and the outlet valve both closed.
Figure 4 shows a schematic diagram of the pump of Figure 2, with the shape memory alloy element contracted, the inlet valve closed and the outlet valve open. Figure 5 shows a schematic diagram of the pump of Figure 2, with the shape memory alloy element relaxed, the inlet valve open and the outlet valve closed.
Figure 6 shows a schematic diagram of a cross-section of a pump according to an embodiment of the present disclosure, the pump comprising a first shape memory alloy elements coupled to a first deformable element and a second shape memory ally coupled to a second deformable element.
Figure 7 shows a schematic diagram of a cross-section of a pump according to an embodiment of the present disclosure, wherein a first end of the shape memory alloy element is coupled to a first part of the deformable element and a second end of the shape memory alloy element is coupled to a second part of the deformable element.
Figure 8 shows a schematic diagram of a top view of a pump according to an embodiment of the present disclosure, wherein the deformable element comprises a first part and a second part.
Figure 9 shows a schematic diagram of a top view of a pump according to an embodiment of the present disclosure, wherein the deformable element comprises a first part and a second part and wherein a first electrical connection and a second electrical connection are connected to the first part and the second part, respectively.
Detailed description
A pump for dispensing fluid is provided. The pump comprises a variable-volume chamber comprising an inlet and an outlet. The chamber is configured to be in fluid communication with a reservoir via the inlet. The reservoir may comprise any source of fluid or volume capable of containing fluid. The reservoir may not be part of the pump, the pump is merely configured to be fluidly connected with the reservoir such that in use, flow of fluid is enabled into the pump. The pump further comprises an aperture and a diaphragm filling the aperture and defining a portion of a boundary of the chamber. The pump further comprises a deformable element adjacent to the diaphragm and a shape memory alloy (SMA) element coupled to the deformable element. The SMA element is configured, on actuation, to deform the deformable element such that the diaphragm bends and the volume of the chamber changes. The SMA element is parallel to a plane of the aperture. The term ‘shape memory alloy (SMA) element’ may refer to any element comprising SMA. SMA material has the property that, on heating, it undergoes a solid-state phase change that causes the SMA material to contract. Thus, applying drive signals to the SMA element, thereby heating the SMA element by causing an electric current to flow, will cause the SMA element to contract. When the electric current ceases to flow, the SMA wire expands to its original length.
In use, increasing the volume of the chamber may draw fluid into the chamber via the inlet. Decreasing the volume of the chamber may expel fluid from the chamber via the outlet.
The pump may further comprise an inlet valve. The inlet valve has an open state enabling flow of the fluid into the chamber from the reservoir via the inlet. The inlet valve has a closed state preventing flow of the fluid into the chamber from the reservoir via the inlet. The pump may further comprise an outlet valve. The outlet valve has an open state enabling flow of the fluid out of the chamber via the outlet and a closed state preventing flow of the fluid out of the chamber via the outlet.
In use, increasing the volume of the chamber may cause a pressure difference between the interior and exterior of the chamber such that the inlet valve opens and liquid is drawn into the chamber. Decreasing the volume of the chamber may cause a pressure difference between the interior and exterior of the chamber such that the outlet valve opens and liquid is expelled from the chamber. In certain embodiments, the inlet valve and outlet valve comprise one-way or nonreturn valves, that open with pressure and fluid movement in a particular direction. The inlet valve may open only in an event that the pressure in the chamber is lower than outside the chamber, i.e. to allow fluid movement into the chamber. The inlet valve may be prevented from opening when the pressure inside the chamber is higher than outside the chamber. The outlet valve may open only in an event that the pressure in the chamber is higher than outside the chamber, i.e. to allow fluid movement out of the chamber. The outlet valve may be prevented from opening when the pressure inside the chamber is lower than outside the chamber. For example, the inlet valve and the outlet valve may each comprise a flap. The flap of the inlet valve may open in a direction into the chamber to allow flow of fluid into the chamber. An end-stop or other mechanism may prevent the flap of the inlet valve from opening in a direction out of the chamber, such that flow of fluid out of the chamber via the inlet valve is prevented. The flap of the outlet valve may open in a direction out of the chamber to allow flow of fluid out of the chamber. An end-stop or other mechanism may prevent the flap of the outlet valve from opening in a direction into the chamber, such that flow of fluid into the chamber via the outlet valve is prevented.
The SMA element may be coupled to the deformable element such that on actuation of the SMA element, the SMA element contracts and the deformable element deforms in such a way that it pushes or pulls the diaphragm, bending the diaphragm. On expansion of the SMA element, the diaphragm may return to its original position. The displacement of the diaphragm may be in a direction not parallel to the SMA element and, therefore, not parallel to the direction of contraction of the SMA element. The displacement of the diaphragm may be in a direction perpendicular to the SMA element and, therefore, perpendicular to the direction of contraction of the SMA element. In certain embodiments, contraction of the SMA element may deform the deformable element such that the diaphragm bends and the volume of the chamber decreases. The pressure in the chamber increases such that, in use, liquid may be expelled from the chamber via the outlet. When the deformable element returns to its undeformed state, the diaphragm returns to its original position, such that the pressure in the chamber reduces. In use, liquid is no longer expelled via the outlet and liquid may be drawn into the chamber via the inlet. In certain embodiments, contraction of the SMA element may deform the deformable element such that the diaphragm bends and the volume of the chamber increases. The pressure in the chamber decreases such that, in use, liquid may be drawn into the chamber via the inlet. When the deformable element returns to its undeformed state, the diaphragm returns to its original position, such that the pressure in the chamber increases. In use, liquid is no longer drawn in via the inlet and liquid may be expelled via the outlet.
The deformable element may comprise one or more elements. In certain embodiments, the deformable element comprises an elongated element adjacent to the diaphragm. For example, the deformable element may comprise a bar or elongate sheet. The SMA element may be coupled to the deformable element at a first coupling point and a second coupling point such that on actuation of the shape memory alloy element, the first coupling point and the second coupling point are pulled towards one another. For embodiments where the deformable element comprises an elongate element, the first coupling point and the second coupling point may be proximate to each end of the deformable element, respectively. Deforming the deformable element may comprise bending the deformable element and/or pivoting the deformable element, or other deformations that can be used to bend the diaphragm.
The deformable element is adjacent to the diaphragm. A first side of the deformable element may be adjacent to the diaphragm The SMA element may be coupled to a second side of the deformable element opposite to the first side. In certain embodiments, the SMA element may be coupled to the deformable element via crimps or other coupling element that allow the SMA element to be held at a certain distance from the deformable element. The distance of the SMA element from the deformable element may affect the extent to which the deformable element deforms for a certain magnitude of contraction of the SMA wire.
Several specific embodiments of a pump of the present disclosure will now be described with reference to the Figures. These examples are not intended to be limiting. In particular, variations in the geometries and relative positions of components may be possible.
With reference to Figure 1 , an example of a pump 100 according to an embodiment of the disclosure is illustrated. A housing 110 comprises the variable-volume chamber. The pump comprises an aperture 120 in the housing 110 and a diaphragm 130, wherein the diaphragm 130 fills the aperture 120. The inlet and outlet are not shown, but may, for example, be located in the lower surface of the housing 110 opposite the aperture 120. The chamber is not visible in Figure 1 , but is located inside the housing 110 below the aperture 120. The pump 100 comprises a deformable element 140 adjacent to the diaphragm 130. The pump 110 further comprises an SMA element 150 coupled to the deformable element
140 and configured, on actuation, to deform the deformable element 140 such that the diaphragm 130 bends and the volume of the chamber changes. The SMA element 150 is parallel to a plane of the aperture 120. The SMA element 150 is coupled to the deformable element 140 via a first crimp 141 and a second crimp 142. In this example, the first crimp
141 and the second crimp 142 are integral to the deformable element 140. The deformable element 140 comprises a portion 143 adjacent to the diaphragm 130. The first crimp 141 and the second crimp 142 are bent upwards with respect to the portion 143 of the deformable element 140 adjacent to the diaphragm 130, such that the SMA element 150 is held above the portion 143 of the deformable element 140 adjacent to the diaphragm 130. In the embodiment illustrated in Figure 1 , on actuation the SMA element 150 contracts and the first crimp 141 and second crimp 142 are pulled towards one another. The deformable element 140 bends such that the diaphragm 130 is pushed downwards. Therefore, on actuation the diaphragm 130 is pushed downwards, increasing pressure in the chamber and, in use, expelling liquid from the chamber via the outlet. When the deformable element
140 returns to its undeformed state, the diaphragm 130 is no longer pushed downwards and returns to its original position, such that the pressure in the chamber reduces. In use, liquid is no longer expelled via the outlet and liquid may be drawn into the chamber via the inlet.
The SMA element 150 may be actuated by applying a current. The first and second crimps
141 and 142 may act as electrical connections for applying the current to the SMA element 150, or the pump may comprise separate electrical connections for applying the current to the SMA element 150. The only conductive path between the first and second crimps is via the SMA element. There is no conductive path between the first and second crimps via the deformable element. In an event that the deformable element is made of electrically conducting material, the electrical connections may be insulated from the deformable element or there may be an insulating portion to the deformable element between the electrical connections.
In certain embodiments, the first and second crimps 141 , 142 may not be integral to the deformable element 140, and may instead be separate elements. In other embodiments, the SMA element 150 may be coupled to the deformable element 140 by other types of coupling elements. The SMA element 150 may be coupled to the deformable element 140 at different positions than shown in Figure 1. The perpendicular distance between the SMA element and the deformable element may vary. In an event that the deformable element is made from an electrically conducting material and that the first and second crimps act as electrical connections, the first and second crimps may be insulated from the deformable element. In an event that the first and second crimps are integral to the deformable element, the deformable element may comprise an insulating portion between the first crimp and the second crimp.
The aperture 120 may have a different shape than that shown in Figure 1. Similarly, the housing 110 may have a different shape than that shown in Figure 1. The pump 100 may be contained within or incorporated into another device or structure, rather than having a separate housing.
With reference to Figure 2, a cross-section of an example of a pump 200 according to an embodiment of the present disclosure is illustrated. An upper housing 211 comprises an aperture 220, the edges of which are labelled. The pump 200 comprises a diaphragm 230, filling the aperture 220. In the example shown in Figure 2, the diaphragm 230 lies on top of the upper housing 211 such that the diaphragm 230 covers the aperture 220. However, other configurations are possible. For example, the diaphragm 230 may not extend beyond the aperture 220 or may not be at the top of the aperture 220. A deformable element 240 is positioned adjacent to the diaphragm 230. An SMA element 250 is coupled to the deformable element 240 via a first crimp 241 and a second crimp 242.
The pump 200 further comprises a variable volume chamber 260. The diaphragm 230 defines a portion of a boundary of the chamber 260. In the example shown in Figure 2, the remainder of the boundary of the chamber 260 is defined by the aperture 220 of the upper housing 211 , a lower housing 212 and a valve arrangement 290. The SMA element 250 is configured, on actuation, to deform the deformable element 240 such that the diaphragm 230 bends and the volume of the chamber changes.
The chamber 260 comprises an inlet 270 and an outlet 280. The pump 200 further comprises an inlet valve 271 and an outlet valve 282. In Figure 2, the inlet valve 271 and the outlet valve 281 are each shown in their closed states. Dashed lines indicate the open state 272 of the inlet valve 271 and the open state 282 of the outlet valve 281. In the example illustrated in Figure 2, a valve arrangement 290 comprises the inlet valve 271 and the outlet valve 281. The inlet valve 271 and the outlet valve 281 each comprise a flap in the valve arrangement 290. The valve arrangement 290 may comprise a valve diaphragm. The inlet valve 271 is configured such that it can open only in a direction into the chamber 260, as indicated by dashed lines 272. In the pump 200 of Figure 2, the inlet valve 271 is prevented from opening in a direction out of the chamber 260 by the lower housing 212. The inlet valve 271 may otherwise be prevented from opening in a direction out of the chamber 260 by an end-stop or other mechanism. The outlet valve 281 is configured such that it can open only in a direction out of the chamber 260, as indicated by dashed lines 282. In the pump 200 of Figure 2, the outlet valve 281 is prevented from opening in a direction into the chamber 260 by an end-stop 213. The outlet valve 281 may otherwise be prevented from opening in a direction into the chamber 260 by the upper housing 211 or another mechanism. Figure 2 shows the inlet and outlet valves 271 and 281 opening about pivot points proximate to an external edge of the inlet 270 and outlet 280, respectively. In other embodiments, one or both of the inlet and outlet valves 271 and 281 may open about pivot points proximate to an internal edge of the inlet 270 and outlet 280, respectively.
The first crimp 241 and the second crimp 242 are positioned with respect to the deformable element 240 such that the SMA element 250 is held above the deformable element 240, opposite to a side of the deformable element adjacent to the diaphragm 230.
In the embodiment illustrated in Figure 2, on actuation the SMA element 250 contracts and the first crimp 241 and second crimp 242 are pulled towards one another. The deformable element 240 bends such that the diaphragm 230 is pushed downwards. Therefore, on actuation the diaphragm 230 is pushed downwards, increasing pressure in the chamber 260 and, in use, expelling liquid from the chamber 260 via the outlet 280. When the deformable element 240 returns to its undeformed state, the diaphragm 230 is no longer pushed downwards and returns to its original position, such that the pressure in the chamber 260 reduces. In use, liquid is no longer expelled via the outlet 280 and liquid may be drawn into the chamber via the inlet 270.
With reference to Figures 3 to 5, operation of the pump 200 shown in Figure 2 will be described. Figure 3 shows the pump 200 in an initial state. The SMA element 250 is not contracted, and the deformable element 240 is in its undeformed state. The diaphragm 230 is not bent. The inlet valve 271 and outlet valve 281 are both in the closed state. In use, the chamber 260 contains a liquid. Figure 4 shows the pump 200 with the SMA element 250 in a contracted state. The deformable element 240 is deformed, pushing the diaphragm 230 into the chamber 260, reducing the volume of the chamber 260. The pressure in the chamber 260 increases relative to the pressure in the outlet 280, causing the outlet valve to open into its open state 282. In use, liquid will be expelled from the chamber 260 via the outlet 280. The inlet valve 271 is prevented from opening to allow liquid to be expelled via the inlet 270, and remains closed. In Figure 4, the diaphragm 230 is illustrated as resting on the end stop 213. This may not be the case. Figure 5 illustrates the pump 200 once the SMA element 250 has relaxed and is no longer contracted. The deformable element 240 returns to its undeformed state, and the diaphragm 230 returns to its unbent state. The volume of the chamber 260 increases, so the pressure in the chamber 260 is lower than the pressure in the inlet 270 and the outlet 280. The outlet valve 281 returns to its closed position. The outlet valve 281 is prevented from moving beyond the closed position. The inlet valve moves to its open state 272. In use, liquid is drawn into the chamber 260 via the inlet 270. This cycle may be repeated, with the SMA element 250 being sequentially contracted and allowed to relax. In this way, liquid may be drawn into and expelled from the pump 200. In an event that the pump 200 is left in the state shown in Figure 5 for a period of time, the inlet and outlet valves may remain in the positions shown. Otherwise, the inlet valve 271 may return to its closed position such that the pump 200 is in the state shown in Figure 3. The inlet valve 271 may relax back to its closed position as a result of the pressure in the chamber 260 equalising with the pressure in the inlet 270, or may close as a result of a biasing force. The biasing force may be provided by the inlet valve itself or by a separate resilient biasing member.
Before use, the pump 200 may be primed to add fluid to the chamber. After manufacture of the pump 200 and before use, liquid may be injected or otherwise placed in the chamber 260. In use, the pump 200 may begin in the state shown in Figure 3, with fluid contained in the chamber 260.
The pump 200 may be primed by operation of the pump 200. The SMA element 250 may be actuated such that the diaphragm 230 is pushed down, as shown in Figure 4, without any fluid being present in the chamber 260. When the diaphragm moves up to the position shown in Figure 5, liquid may then be drawn into the chamber 260, priming the pump 200. On the following contraction of the SMA element 250, liquid may be expelled from the chamber 260 via the outlet 280.
The examples shown in Figures 1 to 5 show embodiments in which contraction of the SMA element deforms the deformable element in such a way that the diaphragm is pushed into the chamber, decreasing the volume of the chamber. In use, actuation of the SMA element expels liquid from the chamber, and relaxation of the SMA element draws liquid into the chamber. In other embodiments, contraction of the SMA element deforms the deformable element in such a way that the diaphragm is pulled away from the chamber, increasing the volume of the chamber. In use. actuation of the SMA element draws liquid into the chamber, and relaxation of the SMA element expels liquid from the chamber. With reference to Figure 6, in certain embodiments the pump comprises a first deformable element adjacent to the diaphragm and a first SMA element coupled to the first deformable element. The first SMA element is configured, on actuation, to deform the first deformable element such that the diaphragm bends in a first direction and the volume of the chamber changes. The first SMA element is parallel to a plane of the aperture. The pump further comprises a second deformable element adjacent to the diaphragm and a second SMA element coupled to the second deformable element. The second SMA element is configured, on actuation, to deform the second deformable element such that the diaphragm bends in a second direction and the volume of the chamber changes. The second SMA element is parallel to a plane of the aperture. Actuating the first SMA element may result in an increase to the volume of the chamber and actuating the second SMA element may result in a decrease to the volume of the chamber, or vice versa. Figure 6 shows a cross-section of an example of such an arrangement. Pump 600 comprises a housing 610 and an aperture 620, the edges of which are labelled. The pump 600 comprises a variable volume chamber 625. The pump 600 comprises a diaphragm 630 that fills the aperture 620 and defines a portion of a boundary of the chamber 625. The pump 600 further comprises a first deformable element 640 adjacent to the diaphragm and a first SMA element 650 coupled to the first deformable element 640 via first crimp 641 and second crimp 642. The first SMA element 650 is configured, on actuation, to deform the first deformable element 640 such that the diaphragm bends in a first direction into the chamber 625 and the volume of the chamber decreases. The first SMA element 650 is parallel to a plane of the aperture 620. The pump 600 further comprises a second deformable element 660 adjacent to the diaphragm 630 and a second SMA element 670 coupled to the second deformable element 660 via a third crimp 661 and a fourth crimp 662. The second SMA element 670 is configured, on actuation, to deform the second deformable element 660 such that the diaphragm bends in a second direction out of the chamber 625 and the volume of the chamber increases. The second SMA element is parallel to a plane of the aperture 620. Other arrangements may be used, in which the first deformable element, first SMA element, second deformable element and second SMA element are all external to the chamber.
With reference to Figure 7, cross-section of an example of a pump 700 according to an embodiment of the present disclosure is illustrated. The pump 700 comprises a housing 710, an aperture 720 and a variable-volume chamber 770. The pump further comprises a diaphragm 730 filling the aperture 720 and defining a portion of a boundary of the chamber 770. The pump further comprises a deformable element comprising a first portion 740 and a second portion 750. The pump further comprises an SMA element 760 coupled to the deformable element. The SMA element 760 is coupled to the first portion 740 of the deformable element via a first crimp 741. The SMA element 760 is coupled to the second portion 750 of the deformable element via a second crimp 751. The first and second portions 740, 750 are adjacent to the diaphragm 730 and are partially attached to the diaphragm 730 such that on actuation of the SMA element 760, the first and second portions 740, 750 pull the diaphragm 730 upwards as illustrated in Figure 7. The volume of the chamber 770 increases and, in use, liquid is drawn into the chamber via inlet 780. The pump 770 may comprise an inlet valve, not shown. Upon relaxation of the SMA element 760, the diaphragm 730 relaxes downwards, reducing the volume of the chamber 770 and, in use, causing liquid to be expelled via outlet 790. The pump may comprise an outlet valve, not shown. In the example shown in Figure 7, when the deformable element is in its undeformed state, the diaphragm 730 covers the inlet 780 and the outlet 790 and the volume of the chamber is zero.
As described above, the SMA element may be contracted by applying an electric current. The electric current may be applied to the SMA element via electrical connections. The crimps may provide electrical connections, or separate electrical connections may be used. The electrical connections may be fixed, such that they do not deform on actuation of the SMA element. The electrical connections may be deformable, such that they are movable on actuation of the SMA element. The electrical connections may be positioned away from the aperture, or such that they pass over the aperture. The electrical connections may be connected to the deformable element or may not be connected to the deformable element.
An example of an arrangement of electrical connections is shown in Figure 8. Figure 8 shows a top view of a pump 800, comprising an aperture 810 and a diaphragm 820. An SMA element, not shown, extends between a first crimp 830 and a second crimp 840. A first portion 850 of a deformable element and a second portion 860 of the deformable element are coupled to the first and second crimps 830, 840, respectively. The first and second portions 850, 860 of deformable element are separate, with no electrical connection between them. First and second electrical connections may connect to the first and second portions 850, 860 of the deformable element respectively or to the first and second crimps 830, 840 respectively, without any conductive path being provided between the first and second crimps via the deformable element. In other words, the only conductive path between the first and second crimps is via the SMA element. In this way, the deformable element, being of two parts, does not provide a conductive path between the first and second crimps 830, 840. The first and second portions 850, 860 of the deformable element may be separate, such that actuating the SMA element causes each of the first and second portions 850, 860 to deform independently of the other. The first and second portions 850, 860 of the deformable element may be connected by an electrically insulating portion.
With reference to Figure 9, the first and second electrical connectors 870, 880 of pump 900 may have a bent shape so as to be able to deform with the deformable element. In the example shown in Figure 9, the first and second electrical connections are connected to the first and second portions of the deformable element 850, 860 respectively. The first and second crimps 830, 840 may be electrically connected to the first and second portions of the deformable element 850, 860 respectively.
In the examples provided above, the inlet and outlet are positioned opposite to the diaphragm. The inlet and outlet may be positioned differently. For example, using pump 200 of Figure 2 as an example, the inlet and outlet are positioned opposite to the diaphragm such that a direction of flow of liquid in the inlet and outlet is perpendicular to a plane of the aperture. Instead, one or both of the inlet and outlet may be positioned in a vertical side of the chamber, such that a direction of flow of liquid in the inlet and/or outlet is parallel to a plane of the aperture. Other configurations are also possible.
The examples illustrated in the Figures show the deformable element extending across but not beyond the aperture. Similarly, the length of the SMA element between the points at which is couples to the deformable element is roughly equal to the diameter of the aperture. In other embodiments, the deformable element and/or the SMA element may be larger than or smaller than the diameter of the aperture.
The deformable element may be planar in its undeformed state. In other embodiments, the deformable element may not be planar in its undeformed state. For example, the deformable element may be curved or bent in its undeformed state, such that on actuation of the SMA element the deformable element bends further. Similarly, the diaphragm may be planar in its default state. In other embodiments, the diaphragm may not be planar in its default state. The diaphragm may be domed, such that on actuation of the SMA element the diaphragm is bent to increase the dome or to invert the dome. In certain embodiments, the deformable element may be in contact with the diaphragm in its undeformed state. In other embodiments, the deformable element may not be in contact with the diaphragm in its deformed state, and may make contact with the diaphragm upon deformation. In certain embodiments, the deformable element in its undeformed state may be parallel with the diaphragm in its relaxed state. In other embodiments, the deformable element in its undeformed state may not be parallel with the diaphragm in its relaxed state.
The SMA element is parallel to a plane of the aperture. Contracting the SMA element along its axis deforms the deformable element such that the deformable element bends the diaphragm. The direction of displacement of the diaphragm is perpendicular to the direction of contraction of the SMA element. The magnitude of the displacement of the diaphragm relative to the magnitude of the contraction of the SMA element depends on several factors. For example, the length of the SMA element relative to the diameter of the diaphragm; the perpendicular distance between the SMA element and the deformable element; the perpendicular distance between the deformable element and the diaphragm; and other geometrical variations.
When the SMA actuator returns to its original length, the deformable element returns to its undeformed state. The diaphragm may return to its original shape by one or more of relaxation, biasing properties of the diaphragm, an attachment to the deformable element, or pressure from liquid.
The deformable element may comprise an etched metal component.
With reference to Figure 10, an actuating unit 1090 is described. The actuating unit 1090 is configured to deform a deformable element 1040 and thus bend a diaphragm 1030. Such an actuating unit 1090 may be implemented as part of any of the pumps described herein in order to bend the relevant diaphragm. The actuating unit may be implemented as part of a pump with passive valves, e.g. the embodiments described with reference to Figures 1 to 7, or may be implemented as part of a pump comprising one or more active valves, as will be described with reference to Figures 11 and 12 below.
Turning to Figure 10, the actuating unit comprises a first SMA element 1050 connected between a first crimp 1041 and a second crimp 1042. The second crimp 1042 is connected to a housing 1010. The first crimp 1041 is coupled to the first deformable element 1040. On actuation of the first SMA element 1050, the first SMA element 1050 contracts and the first deformable element 1040 bends in a first direction.
The actuating unit further comprises a second SMA element 1070 connected between a third crimp 1061 and a fourth crimp 1062. The fourth crimp 1062 is connected to the housing 1010. The third crimp 1061 is coupled to a first deformable element 1040. On actuation of the second SMA element 1070, the second SMA element 1070 contracts and the first deformable element 1040 bends in a second direction.
The first deformable element 1040 is integral with (but in some embodiments may be otherwise connected or coupled to) an engaging portion 1044 and a securing portion 1047. The securing portion is attached to the housing 1010. The first deformable element is elongate and is flexible in a direction perpendicular to the direction of elongation (i.e. its longitudinal axis). The engaging portion 1044 is rigid such that when the first deformable element 1040 is bent as a result of contraction of one of the first and second SMA elements 1050, 1070, the engaging portion 1044 is moved up or down. When the second SMA element 1070 contracts, the engaging portion 1044 is moved downwards (as seen in Figure 10) and engages with the diaphragm 1030, thus bending the diaphragm 1030.
When the first SMA element 1050 contracts, the engaging portion 1044 is moved upwards (as seen in Figure 10) and disengages from the diaphragm 1030. The diaphragm may return to its original, unstressed state by one or more of a number of means: as a result of the elasticity of the diaphragm 1030 itself, as a result of a pressure differential across the diaphragm (e.g. as a result of fluid pressure on the other side of the diaphragm) and/or by means of a resilient element such as a spring (not shown) imparting a return force on the diaphragm 1030. In some embodiments, the diaphragm 1030 may be attached to the engaging portion 1044 (e.g. glued or otherwise connected) such that when the engaging portion 1044 moves upwards as a result of contraction of the first SMA element 1050, the diaphragm 1030 is pulled upwards.
As will be described below, the diaphragm 1030 may form part of a boundary of a variable volume chamber in the same way as described with reference to Figure 7. Accordingly, movement of the diaphragm 1030 under action of the actuating unit 1090 may drive fluid flow. Alternatively, the diaphragm 1030 may be adjacent to an aperture in the housing 1010 and bending of the diaphragm 1030 may partially or completely block the aperture, thus controlling fluid flow and acting as a valve.
With reference to Figure 11, a pump 1000 is described comprising three actuating units 1090, 1092 and 1094, each as described with reference to Figure 10 and each shown schematically. The first actuating unit 1090 is adjacent to and drives movement of a first diaphragm 1030 (not shown in Figure 11) which forms part of a boundary of a variablevolume chamber. The second actuating unit 1092 is adjacent to and drives movement of a second diaphragm 1032 (not shown in Figure 11), which opens and closes an inlet valve. The third actuating unit 1094 is adjacent to and drives movement of a third diaphragm 1034 (not shown in Figure 11), which opens and closes an outlet valve. The first, second and third diaphragms may all be integral with one another, such that they are all provided by a single diaphragm which may, for example, be a single sheet of material.
With reference to Figure 12, further details of the pump 1000 shown in Figure 11 are described. Figure 12 is a view along direction A, as shown in Figure 11.
The pump 1000 comprises a diaphragm 1900 which makes up each of the first, second and third diaphragms 1030, 1032 and 1034. Each of the first, second and third diaphragms are each adjacent to a respective engaging portion of an actuating unit 1044, 1044a and 1044b. Each engaging portion is driven to move by respective pairs of SMA elements, as described with reference to Figure 10.
The pump 1000 also comprises a housing 1010. The housing defines a second aperture 1073 which forms part of an inlet valve 1071 which is in fluidic communication with an inlet 1070. The second actuating unit 1092 is actuated (by contracting the second SMA element - see figure 10 - of the second actuating unit 1092) to bend the second diaphragm 1032 downwards, which engages with the housing 1010 at the second aperture 1073 and blocks the second aperture, thus closing the inlet valve. Liquid is thus prevented from flowing from the inlet 1070 into the chamber 1060, which is described below. To open the inlet valve, the first SMA element is contracted (see figure 10), which releases the diaphragm. Fluid pressure inside the chamber forces the diaphragm back to its neutral state and liquid is able to flow from the inlet into the chamber 1060. In some embodiments, as described above, the engaging portion may be attached to the diaphragm in which case movement of the engaging portion upwards would pull the diaphragm upwards.
The housing also defines a third aperture 1083 which forms part of an outlet valve 1082 which is in fluidic communication with an outlet 1080. The third actuating unit 1094 is actuated to open and close the outlet valve in the same way as described for the inlet valve.
The housing 1010 also defines a variable-volume chamber 1060 which comprises an aperture which is filled by the first diaphragm 1030. The aperture is defined by the housing 1010. Actuation of the first actuating unit 1090 bends the first diaphragm and changes the volume of the chamber 1060. By contracting the second SMA element (see figure 10) of the first actuating unit 1090, the engaging portion is driven downwards, thus bending the diaphragm. By contacting the first SMA element of the first actuating unit 1090, the engaging portion is driven upwards and the diaphragm also moves upwards and returns to its neutral position (e.g. as a result of fluid pressure in the chamber 1060).
With reference to Figure 12, operation of the pump 1000 will be described. Figure 12 shows the pump 1000 in an initial state, in which none of the diaphragms 1030, 1032 and 1034 are bent. None of the SMA elements of the first, second and third actuating units 1090, 1092 and 1094 are contracted so each respective deformable element is in its undeformed state. and each respective engaging portion is in a neutral state. The inlet valve 1071 and outlet valve 1081 are both in the open state. In use, the chamber 1060 contains a liquid.
Before use, the pump 1000 may be primed to add fluid to the chamber. After manufacture of the pump 1000 and before use, liquid may be injected or otherwise placed in the chamber 1060.
The pump 1000 may be primed by operation of the pump 1000. The first actuating unit 1090 may be actuated such that the diaphragm 1030 is pushed downwards, as seen in Figure 12, without any fluid being present in the chamber 1060. The outlet valve is closed and the diaphragm 1030 is released. When the diaphragm 1030 moves upwards again, to the position shown in Figure 12, liquid may then be drawn into the chamber 1060, priming the pump 1000. The inlet valve is then closed and the outlet valve is opened. The first diaphragm 1030 is then bent, reducing the volume of the chamber 1060. The pressure in the chamber 1060 increases and fluid is expelled from the chamber 1060 via the outlet 1080.
The outlet valve is then closed and the inlet valve is opened. The first diaphragm 1030 is released (by actuation of the first SMA element of the first actuating unit 1090) and returns to its unbent state. The volume of the chamber 1060 increases, so the pressure in the chamber 1060 is lower than the pressure in the inlet 1070. In use, liquid is drawn into the chamber 1060 via the inlet 1070. This cycle may be repeated. In this way, liquid may be drawn into and expelled from the pump 1000.
The pumps described above can each be used in several modes of operation. The pumps can at least be used in a non-resonant pumping mode, a resonant pumping mode and a dosing mode.
In the non-resonant pumping mode, the diaphragm may be driven up and down by repeatedly actuating the SMA element. The SMA element may be actuated such that it contracts. The SMA element is then allowed to expand, before being contracted again, and so on. As the diaphragm is driven up and down, the volume of the chamber increases and decreases such that fluid is pumped into and out of the chamber via the inlet and outlet valves. The rate of fluid flow may be adjusted by adjusting the frequency of the displacement of the diaphragm and/or by adjusting the amplitude of the displacement of the diaphragm.
In the resonant pumping mode, the deformable element has a resonant frequency or frequencies. When designing the device, properties of the pump such as mass and/or spring constant of the deformable element may be chosen so as to provide a desired resonant frequency or frequencies. During operation, the SMA element can be driven at a frequency that is close to a resonant frequency or related to the resonant frequency (e.g. a harmonic). Driving the displacement of the deformable element at a resonant frequency reduces the power required to sustain a given amplitude of motion. The flow rate can then be adjusted by varying the amplitude of motion while adjusting or maintaining the frequency of motion to preserve the desired relationship with the resonant frequency(s).
In the dosing mode, the operation of the pump may be a single stroke (i.e. single actuation of the SMA element) to deliver a controlled volume of liquid. A pump being used in dosing mode may not have inlet and outlet valves. The volume is related to the magnitude of the displacement of the diaphragm, which in turn is related to the magnitude of contraction of the SMA element. The magnitude of contraction of the SMA can be controlled, which allows the position of the diaphragm to be accurately controlled.
In any of the modes, the magnitude of contraction of the SMA element may be controlled, thereby allowing control of the magnitude of the displacement of the diaphragm. The contraction of the SMA element may be controlled by varying the current passing through the SMA element and, therefore, the temperature of the SMA element. The contraction of the SMA element is also affected by the length of the SMA element when not contracted, and the resistance of the SMA element. The magnitude of the displacement of the diaphragm may also be controlled by controlling the frequency of actuation of the SMA element.
The above-described pumps comprise at least one SMA element. The SMA element may be described as an SMA wire. The SMA element may have any shape that is suitable for the purposes described herein. The SMA element may be elongate and may have a round cross section or any other shape cross section. The cross section may vary along the length of the SMA element. The SMA element might have a relatively complex shape such as a helical spring. It is also possible that the length of the SMA element (however defined) may be similar to one or more of its other dimensions. The SMA element may be sheetlike, and such a sheet may be planar or non-planar. The SMA element may be pliant or, in other words, flexible. In some examples, when connected in a straight line between two components, the SMA element can apply only a tensile force which urges the two components together. In other examples, the SMA element may be bent around a component and can apply a force to the component as the SMA element tends to straighten under tension. The SMA element may be beam-like or rigid and may be able to apply different (e.g. non-tensile) forces to elements. The SMA element may or may not include material(s) and/or component(s) that are not SMA. For example, the SMA element may comprise a core of SMA and a coating of non-SMA material. Unless the context requires otherwise, the term ‘SMA element’ may refer to any configuration of SMA material acting as a single actuating element which, for example, can be individually controlled to produce a force on an element. For example, the SMA element may comprise two or more portions of SMA material that are arranged mechanically in parallel and/or in series. In some arrangements, the SMA element may be part of a larger SMA element. Such a larger SMA element might comprise two or more parts that are individually controllable, thereby forming two or more SMA elements. The SMA element may comprise an SMA wire, SMA foil, SMA film or any other configuration of SMA material. The SMA element may be manufactured using any suitable method, for example by a method involving drawing, rolling, deposition, sintering or powder fusion. The SMA element may exhibit any shape memory effect, e.g. a thermal shape memory effect or a magnetic shape memory effect, and may be controlled in any suitable way, e.g. by Joule heating, another heating technique or by applying a magnetic field.
There is also provided a method of dispensing fluid using a pump according to the present disclosure. The method comprises actuating the shape memory alloy element such that the volume of the chamber changes from a first volume to a second volume and liquid flows through the chamber in a first direction. The method further comprises allowing the shape memory alloy element to relax such that the volume of the chamber changes from the second volume to the first volume and liquid flows through the chamber in a second direction.
The method may further comprise repeating the steps of actuating the shape memory alloy element and allowing the shape memory alloy element to relax.
There is provided a pump for dispensing fluid, the pump comprising a variable-volume chamber comprising an inlet and an outlet, wherein the chamber is configured to be in fluid communication with a reservoir via the inlet. The pump further comprises an aperture. The pump further comprises a first diaphragm filling the aperture and defining a portion of a boundary of the chamber. The pump further comprises a first deformable element adjacent to the first diaphragm. The pump further comprises a first shape memory alloy element coupled to the first deformable element and configured, on actuation, to deform the first deformable element such that the first diaphragm bends and the volume of the chamber changes. The first shape memory alloy element may be: parallel to a plane of the aperture (or to a plane in which the first diaphragm lies when in a neutral state), or
- At an acute, non-zero angle to the plane of the aperture (or to a plane in which the first diaphragm lies when in a neutral state). The pump may have any of the features described herein, for example the features set out in the dependent claims.